Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with a graphical user interface according to the new design.

The outermost broken line in the FIGURE illustrates a display screen or portion thereof and forms no part of the claimed design. The remaining broken lines represent elements of the display screen or portion thereof with a graphical user interface that form no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 